Estrella Geniss

The South Mountains of central Arizona
are a typical, but geologically simple, metamorphic
core complex. The western half of the
range is underlain by Precambrian metamorphic
and granitic rocks, whereas the eastern half
is primarily a composite middle Tertiary pluton.
The Precambrian terrane is composed of
two rock units, Estrella Gneiss and Komatke
Granite, both of which were involved in a
major episode of middle Proterozoic metamorphism
and deformation that produced a steep
crystalloblastic foliation. The composite Tertiary
pluton has three semicontemporaneous
phases: (1) South Mountains Granodiorite, the
oldest and most widely distributed phase; (2)
Telegraph pass Granite; and (3) Dobbins Alaskite.
Both the precambrian terrane and the
composite Tertiary pluton have been intruded
by numerous, north-northwest-trending, middle
Tertiary dikes.

Publication Date

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